The present invention relates to a mains-operated device for curing by light polymerizable dental material wherein the device comprises a light source including a filament and a reflector which extends on a side of the filament remote from the dental material, wherein the reflector is transmissive for infrared radiation and is positioned in a cooling air flow of the cooling fan of the device.
Light-curing devices for dental applications are either in the form of mains-operated devices or battery-operated devices. While battery-operated light-curing devices have advantages with respect to their manipulation, especially when they are in the form of hand-held apparatus, since operation without an attached cable is possible, mains-operated light-curing devices have the advantage that they are independent of the securing means of the battery or accumulator, do not require recharging and operating time monitoring while, at the same time, their luminance is uniform, i.e., independent of the charge state of the accumulator, and furthermore, the luminance is much greater.
Light sources for mains-operated light-curing devices are usually in the form of conventional low voltage cinema projection lamps having either a reflector attached to the housing or an integrated reflector as known from German Offenlegungsschrift 28 41 112. Due to the considerable heating of such a lamp it must be cooled intensively which requires a correspondingly powerful fan. The cooling air flow of the fan is designed such that it will not impact the treatment area of the device. However, the cooling air stream exiting at the rearward end will bother the dentist using the device when the light curing device is a hand-held apparatus.
When employing a mains-operated light-curing device, a transformer must be used which is usually provided in a separate base station whereby the supply cable for the hand-held apparatus extends between the hand-held apparatus and the base station. Especially for high output devices, the transformer thus emits a correspondingly strong electromagnetic field which is undesirable in dental practices because other sensitive devices with sensors can be impeded in their operation and diagnostic results of these devices can be negatively affected. Accordingly, for correspondingly strong transformers an insulation of the housing of the supply station is desirable which, however, would impede proper cooling and is therefore not realized in practice. It is suggested to separate the supply station especially from the hand-held apparatus and separately from other diagnostic tools which, however, requires a correspondingly long supply cable which is in turn undesirable with respect to manipulation of the device.
Therefore, it has been suggested to replace the conventional transformers with a power pack. They allow reduction of the weight of the supply station, but emit radiation of a higher frequency which must then be shielded in order to avoid operational malfunction of other devices. Also, such power packs require a plurality of electronic components and their manufacture is complicated because an adaptation to selected specifications is required.
A disadvantage of light-curing devices of the prior art, when operated by mains, is that the employed transformer is costly. The presence of the base station also, in general, impedes the operation of a dental practice since such a base station is an additional device which is required but can be viewed as an auxiliary device for the pistol-shaped light-curing device.
The light-curing devices, especially when they are hand-held apparatus, advantageously employ a so-called soft start. The electrical power supplied to the light source is slowly increased, for example, over a time period of 4 seconds, in order to prevent that a patient would be accidentally blinded when abruptly the full output of the light source would be released. The soft start allows the patient to close his eyes or to turn his head.
In addition to the transformer, a corresponding electronic is required in the supply station which requires rectification and smoothing of the alternate current supplied by the transformer and thus further increases the control expenditure. Also, in the known light-curing devices with soft start the output electronic must be provided within the supply station. In high-quality light-curing devices the detection of the emitted light output is required at the hand-held apparatus which requires a control circuit extending through the supply cable.
Dental material to be cured by light polymerization must be completely hardened during the polymerization cycle in order to prevent that the filling remains somewhat soft, thus causing gap formation at the edges which could result in secondary tooth decay.
Due to their excellent manipulation properties, dentists prefer polymerizable dental materials even for complex fillings with a respective great filling depth. For such fillings, the risk of incomplete polymerization of the areas deep in the tooth is even more increased. Experiments have shown that the known light-curable dental materials which have a minimal shrinkage during polymerization absorb a portion of the light output required for polymerization so that with increasing depth the amount of light available for polymerization decreases and thus its curing powers due to absorption of the UV portion of the light. This effect cannot be compensated by extending the polymerization period or can be compensated only unsatisfactory especially since a long polymerization time is cumbersome for the patient as well as the dentist.
It is therefore an object of the present invention to provide a light-curing device of the aforementioned kind which allows for a considerably reduced polymerization period, but, at the same time, ensures safe light curing of areas deep within the tooth. They are to be manufactured relatively inexpensively and should have improved handling.